ChannelSelector improvements.

* Updated images for collapse/show button;
* Updated animations;
* Some other small UI improvements;
* Added possibility to collapse element by clicking "ESC" key
  either on the component itself or on the TextEditor.

* Created SlicerChannelSelectorComponent class which holds inside
  all ChannelSelector's parser related components and which
  takes responsibility for parsing selected range, etc.
* Added possibility to collapse parser related components.
* Added animations.
* UI improvements.
* Minor bugs fixes.

followed instructions by Christopher Stawarz in
https://open-ephys.atlassian.net/wiki/display/OEW/Plugin+build+files

Mac path changes

Set MACOSX_DEPLOYMENT_TARGET (i.e. the minimum supported OS X version) to 10.9.  Pass -Wpartial-availability to the compiler so it will warn about usage of API's that aren't available on all supported OS X versions.  Removed /opt/local and /usr/local from OS X header and library search paths, as they're used only by specific plugins and not needed generally.

On OS X, the default directory for files explicitly saved/loaded by the user is now ~/Documents/open-ephys.  Added CoreServices::getDefaultUserSaveDirectory(), which returns ~/Documents/open-ephys on OS X and the current working directory on other platforms.

On OS X, the default data directory is now ~/Documents/open-ephys, which is created if it doesn't exist

pulling from inproved-lfp-rendering to main dev branch

Improved lfp rendering

this should reduce the impact of the remaining 1px plot issue until we
track it down

non plugin specific class defs should not go into the plugin specific namespace

this range makes saturation bounds visible, useful for testing if
behavior rigs work etc.

the correct value seems to be 6389 for this gain setting etc. 2do:
double check that

though there is still a small display issue if the end of the display
buffer is hit because now only 1-2samples are associated with the pixel
and this causes the min/max and histogram displays to look odd.
shouldn’t be a big issue in real applications but worth fixing when we
inevitably refactor this whole plugin.

Merge branch 'master' and appropriate needed fixes of https://github.com/priyanjitdey94/plugin-GUI into development

Kwik changes and improvements