Adding a CodeMirror option for controlling how long the ternTooltip should be visible before closing

... and export (via defineExtension) a method to explicitly trigger
linting from user code.

Closes #3409

Closes #3410

Issue #3401

Issue #3395

Issue #3395

Issue #3387

See http://discuss.codemirror.net/t/tern-webworker-causing-hint-flickering/300

When something is redraw, we definitely need to do the consistency-
ensuring that is done by a display update.

Issue #3387

Issue #3337

Closes #3384

Issue #3337
Issue #3338

Issue #3357

Tern completion for required module returns name (module wuith quote)
and displayName (module without quote). This PR gives the capability
to display completion for required module without quote.

Issue #3372

Reference: https://groups.google.com/forum/#!msg/codemirror/uRUuqXimqj0/mn3Lmdkab18J
Rewritten to match the style of the Verilog mode

I noticed that the image that accompanies auto-completion suggestions
when the tern addon is active gets cut slightly, because the default
line height is slightly smaller than the image height.

This change above ensures that the line height is bigger, hence
ensuring that the image is fully shown.