Toggle to show motif search drop-down

[bestchai]

Currently the motif search and text search are integrated -- the motif search drop-down shows up whenever the user clicks in the search text box. This drop-down is intrusive and not necessary when the user is performing a text search.

Instead, add a toggle to display the motif search drop-down. This toggle can look like a graphic that can be clicked to show the drop-down, or clicked to hide the drop-down. So, the graphic needs an "enabled" and a "disabled" view. Alternatively, we can use a button with text like "Show motif search" and "Hide motif search".

The are some slightly tricky semantics that have to be worked out to have this work properly -- if the user pastes a #motif string then the motif drop-down should be shown, if they paste a keyword search then the motif drop-down should be closed, etc.

[Issue created by bestchai: 2014-08-18]
[Last updated on bitbucket: 2014-08-26]