enabled pressing the enter key in the Textbox to initiate the Search.
refined logic slightly on checking for missing search text.
Removed `checked` as default for "Fine Exact Matches Only"
make the default highlight colors more consistent.
make the point highlight fill more transparent.
add check to exclude feature graphics with missing coordinates.
add check to only zoom to extent of all features when there actually is
an extent.
Merge pull request #203 from cmv/feature/enter-key-for-find-widget

Feature/enter key for find widget