Bug 425227 - Orion Editor Content Assist Improvements
- Added support for HOME and END keys
- Added handling for cases when first proposal in list is unselectable, e.g. a section title such as "Templates"
- Removed duplication of state between the ContentAssistMode and ContentAssistWidget. "proposals" and "selectedIndex" now only exist in ContentAssistMode.
- Refactored iteration through popup items and improved performance of item selection.
- Added support for making a visual distinction between name of proposal and its description.
- If there's only one proposal apply it immediately instead of showing popup

--Signed-off-by: Elijah El-Haddad <elijahe@ca.ibm.com>
Bug 425227 - Orion Editor Content Assist Improvements
- Made popup look slicker: better shading, rounded corners, got rid of scroll bars unless popup is hovered
- Distiguished between the name of a proposal and its description where possible for templates, HTML and Javascript content assist.
- Disabled non-inferred proposals by default

--Signed-off-by: Elijah El-Haddad <elijahe@ca.ibm.com>