ConfigFileParameters: fix method order

See: http://developer.imagej.net/coding-style
ConfigFileParameters: remove deprecated logic

The ConfigFileParameters class was performing operations that really
need an ImageJ context, but without having one. So now the class is
Contextual, making it much more straightforward for it to query the
ImageJ application version, use a proper LogService, etc.

The OptionsMemoryAndThreads plugin has been updated accordingly to
lazily pass the context to its ConfigFileParameters helper instance.
CommandFinderPanel: be defensive about file paths

It is possible that the associated file of a class can come back
null. It hasn't happened in practice before, but I encountered the
problem when I had stale SezPoz annotation metadata (thanks,
Eclipse!). In any case, it is better to be defensive, so that just
in case a weird situation comes up, the Command Finder UI will
simply show the file path as blank, rather than an NPE being thrown.
DumpStack: add missing final keywords
DumpStack: add Ctrl+\ keyboard shortcut!
Use caret for control keyboard shortcuts

This is more succinct. It will also be necessary due to a pending
change in SciJava Common which will now only swap in meta for '^'
(not for "control " or "ctrl " anymore).