Autocompletion

[gak]

Allow autocompletion when users type.

For example, when you focus the cursor on the input immediately a list of keys are shown in a drop down. When the user starts typing it drills down and reduces the options.

Once the user gets to the colon, e.g. key:, a set of values could be displayed.

Need to also consider previously searched terms for the user to reuse. Maybe it can be part of the autocomplete functionality, or elsewhere.

#44 will help with this.