Slim Query/Table Table: manage variables assignment in VariableStore

This is idential to pull request 525.
Only one line is different but needs no change in the protocol. Just
additional library functions.
removed dead code
additional keyboard shortcuts

Added more keyboard shortcuts. Especially on test and edit page to allow
the test, edit, save, test cycles to be done only with the keyboard and
without the mouse.
Revert "removed dead code"

This reverts commit d09fb4ce66cbc536072a0ac952a986a7ad59dbcb.
Revert "Slim Query/Table Table: manage variables assignment in VariableStore"

This reverts commit 57fc55eeb71f10aafe82fae4fe7e12b1f6ba95a5.
Merge pull request #549 from six42/keyboard

Additional Keyboard Shortcuts
Fix tests and styling issue in bootstrap theme.