highlighting was still broken for bookmarks that werent alphanumeric
w/underscores. Also, highlight the path parts of the bookmarks table as
"normal" so they dont demand as much attention

now the only rule is that they cant contain spaces

The tree filters for files/hidden-files/bookmarks now operate off tab
local variables which default to the global variables when a nerd tree
is initialised in the tab. Note: the file-filter already operated in
this way.

This means that each tree/tab has its own filter settings that are
initialised to the users preferences as specified by the global
variables, but can be altered independently of the other trees/tabs

We needed to change how the bookmark name caching was done to work with
the new path-display-string caching. It has now been merged into path
string caching.

when the path object is refreshed, force the display string to be
recalculated

if the bookmark wasnt cached in the tree an exception was being thrown
that wasnt caught

instead of using 2 options to specify the position of the tree, just use
NERDTreeWinPos and set it to "left", "right", "top", "bottom"

when you hit t/T on a bookmark a new tab is opened and, if the bookmark
is a dir, a nerd tree is opened for that dir. If the bookmark is a file
then just open the file

when the user activates a file bookmark open that file in the previous
window (i.e. do the 'o' mapping)

hitting 'o' or clicking a bookmark will now make that bookmark to the
new tree root, in the same way that :BookmarkToRoot does

with some slight modifications

if the nerd tree window is the only window open when the user opens a
file, the file will be opened in a new split. Previously that meant the
two windows would take up half the screen each.

take &scrolloff into account when restoring the window position when
recreating the nerd tree window

store the old nerd tree window size as a tabpage local variable and
restore it when reloading the tree window

the <tab> mapping creates a new window, and we previously resized the
nerd tree window at the same time

This reverts commit 6334e99192.
Opening files silently causes vim to hang if the file is already open by
another vim instance (it tries to print out the swap file
message/options but it cant).

The quickhelp had some trailing whitespace, this was removed and a help
highlight pattern had to be changed to fit. Also, there was another
trailing space the s:RenderView() function.

previoulsy, <c-k>/<c-j> did magic stuff if the selected node was a file.
i.e. jumped to the parent/parents next sibling. I chose to remove this
behaviour as it is more confusing than helpful.

previously we were escaping when deleting files, and this was causing
the operation to fail