Git: Update exclude file and coloring

Add debbuild by-products into global exclude file and update colors used by git
commands to look better in bright xterm.
Vim: Add term variable change when run under screen

When Vim runs under screen, the CTRL+PGUP does not behave correctly making
jumping between tabs difficult. This setting fixes the behaviour.
Vim: Add asciidoc bundle
Vim: Custom bundle installation
Vim: Add custom bundle with modified colorscheme

The main modifications:

 * use cyan color for number, fold and sign background
 * change Spell* highlighting to use underline instead of background

These modifications will allow for spellchecking in strings (which have red
foreground color :-)) and better visual diferentiation of left pane with line
numbers.