Fixes/cleanups

Code clean ups, makes various funcs easier to work on... Also includes a few (small) speed ups, and some bug fixes.

• fixes pkg_uninstall() failure to get dependent packages
• fixes in get_pkg_filename: return 1 package name or nothing
• fix: run post install stuff in a sub shell
• fix issues ( think!):
  • 87 (suppress errors regression)
  • 90 (search local *.files first in is_installed_pkg()
  • 89 (weak repo name matching in get_dep_entry)
• (minor) speedups in package name and dep resolution, checking package status (installed or not)
• re-organised code in various functions:
  • clearer logic and ordering
  • moved code out of if blocks where possible, less indentation
  • removed unnecessary code