Run apk_solver_solve once with all args as dependencies instead of
running apk_solver_solve for each arg. This is neccesary so the
install_if calculation is done correctly.

This unloads --force as several of the things are really not wanted
together. E.g. --force-refresh is a lot different from --force-broken-world
and doing --force to get the other might introduce unwanted behaviour.

--force is still kept for backwards compatibility and it enables
most things --force was used for.

This reduces function pointers in heap, and unifies how the
io functions are called.

The virtual package provider still needs to be explicitly
given on command line.

which will delete any .apk package on output directory that were
not downloaded by fetch

this allows apk fetch to incrementally build repositories for
binary images

preserve [am]time for all packages and indexes. this fixes the caching
error that 'apk update' is after new index is generated, but before
the used mirror is synchronized. this caused local apkindex timestamp
to be newer than file in mirror, when in fact it was outdated index.

this also fixes fetched files to have build timestamp so that files
going to .iso or custom images have proper timestamps (rsync with
appropriate --modify-window now works)

In case all applet arguments are packages names (that is are not
including wildcards), return error if they do not match to some
package.

Add also a new 'commit' group that is the common options
for all applets that can commit package changes.

This reverts commit a99bedba.

Prevent the progressbar and status messages to mess up stdout.

Acked-by: Natanael Copa <ncopa@alpinelinux.org>

ref #511

- let the apk_print functions deal with the forced print itself. We
  avoid that the callbacks need to deal with the force flag. We can
  also get rid of the APK_PRINT_PROGRESS_* defines.

- let the reader of --progress-fd decide how often things are updated
  rather than having a fixed granularity off 1/100 (percent)

- avoid detect screen size and percent/bar calculations in case the
  --no-progress was given

- track satistics for both the ascii bar and percent info and update bar
  only if either percent or bar changes. This makes the bar go smoother
  when width is wider than 100 chars and it makes the percent counter
  go smooth when screen width is less thann 100 chars. It also
  simplifies the callbacks as they no longer need to deal with update
  granularity.

Fixes also 'fetch' applet to prefer copying/linking to files from
cache if possible.

Implementing basic dependency handling, install_if and awareness
of pinning.

Solver will now never report partial solution where a conflict
constraint is not satisfied. The is because with --force we might
install the partial solution; and if conflicted packages were to
be installed we might have extra trouble.

in preparation for provides support. implements also some
dependency satisfaction helper routines.

ref #574.

still todo:
  - 'fix' is missing
  - 'del -R' does not work
  - 'upgrade' does not do self-upgrade first

... and a lot of testing.

broke after making the version field an atom because the printf
was not updated accordingly.

The version now needs to be initialized atom always, since it's
dereferenced in various places.