Tweak searching

Turn on hlsearch, and bind ^[u in normal mode to :nohlsearch.

Remove some disabled or bad mappings.

Add highlight groups for the ,h[123] maps, and add maps to clear the
match highlighting.

Fix the ,B BlockColor command.
Rewrite BlockColor command
Tweak mapping definitions for BufExplorer, Command-T, TagBar
Change ^L mapping

Change the ^L mapping to ,r and add a new ,l mapping that does the
default ^L. This allows ^L to be the window movement shortcut that was
defined earlier.
Update bundle/tagbar
Update bundle/bufexplorer, remove <F3> mapping

Replace bufexplorer with a submodule.

Delete the <F3> mapping, just use the default ,be mapping.