Cosmetics
Implemented helper pkgPatch for applying patches

This function automatically determines the correct patch level of a
patch and applies it.

The default function src_prepare() automatically passes the PATCHES
array to pkgPatch (again, very similar to ebuild).
Fix pkgConfigureOption options with value (e.g. --with-*-dir=VALUE)
Display command invocations underlined and already at verbosity level 2
Removed unnecessary SGR clearing
Several improvements for package feature support
Misc documentation of README / TODO / config sample
Added support for including multiple config files
Show whether feature value is empty
Updated submodule pkg