This changeset allows the second parameter of the Bundle command (a
dictionary) to override bundle object fields that come from parsing the
bundle spec. This means that
 Bundle 'abolish.vim', {'name' : 'abo'}
will be installed in a bundle directory named 'abo', rather than
'abolish.vim', which is the name parsed from the bundle spec.

By storing bundles in a sorted dictionary (dictionary + list of keys),
the bundle does not need to be reparsed during installation if it has
already been initialised, and any additional options passed in the
original command are kept.

This changeset is also an initial attempt to stabilise the name vs
spec naming convention, where a bundle spec is whatever is used to
specify a bundle, be it a name, user/name, full uri, etc., and name is
the name of the bundle that will become a directory under the bundles
directory.

closes #1

Also save/restore input so potential mappings aren't broken.

Prevents the user from having to type a space before the search term.

- closes #80

- use `redraw` instead `redraw!`
- closes #90

- to avoid accidental removal

- so it better reflects the content

- do not clutter up ~/

- not sure if there's a need for log file in predefined location
- installer is verbose enough to signal errors

- to avod error when deleting nonexisting buffer

- show installation destination

- batch process just iterates through the lines and calls specified
action
- individual actions give visual feedback aswell
- allow Helptags command as a part of installation process

- merge with view()
- no need for having both

- log is global array so log can be viewed any time
- log gets written to a defined location ~/.vim-vundle/vundle.log
- TODO: write log changes as they happen

BundleInstall sources the current vimrc in order to reload all Bundles
in order to consider new Bundles that might have been added by the user
directly on their vimrc file. This, however, should not be Vundle's
responsibility, changes in vimrc should not be applied unless it is
re-sourced explicitly by the user.

This makes Vundle use the known list of Bundles for installation.

- but don't like it

- TODO: refactor: extract common code

Installer buffer is marked as modified after each installation. Mark it
as nomodified so that no warnings are shown when the buffer is closed.

- Bundles is not a good name for search
- BundleSearch undeprecated
- TODO: repurpose :Bundles cmd