Noissue - Remove dead headers

Noissue - Remove dead headers

Remove PluginTypedef.h, which had no code at all.

Remove AdblockPlusTab.{h,cpp}, which only declared/defined a trival subclass
of PluginTabBase. Moved the definition into PluginTabBase.h.

Remove PluginTab.h, which only included other headers. Change all the
inclusions of PluginTab.h to PluginTabBase.h, which now has exactly the same
effect.

[Eric, 2015-02-14 18:53:09]

This is the first part of a refactoring to clean up definition of CPluginTab.
It's currently declared as a trivial subclass of CPluginTabBase, which itself
has no other subclasses. What this change does is to get rid of the extraneous
files involved in the definitions; it does not actually change the definitions. 

This refactoring is split in parts in order to make the review process more
feasible. What follows this step is a lot of renaming. Since that's a lot of
text changes, it's easier to follow if it's done separately. In particular,
combining the renaming here would cause difficulties with PluginTab.h. It's old
content was trivial. After the whole refactoring is done, it will basically be
everything in PluginTabBase.h. We won't get good diffs out of this review tool
if we were to combine these stages.

The elimination of PluginTypedef.h is tagging along for the ride.

[sergei, 2015-02-14 23:14:27]

LGTM

[Oleksandr, 2015-02-17 12:22:04]

LGTM