Set equivalent projection when possible (see #177)

We want to set the equivalent projection even if the bbox isn't advertised in the same.
Support for ArcGIS REST layers
Add a dropdown to NewSourceDialog for selecting between source types (WMS, ArcGIS REST).
Clean up a few lines
Tweak text
fix typo
work in progress on a TMS source
get things to work with MapProxy TMS, but needs more clean up
a bit of clean up
use a second request to get serverResolutions and extension correctly
ability to add a custom TMS
be liberal and also accept a tileMap endpoint such as http://hiu-maps.net/hot/1.0.0/basemap_a_v1/
error handling
restore original example and add a note to the docs about the usage
latest OpenLayers to get TMS capabilities parser
Merge pull request #194 from bartvde/tms

Allow adding of TMS in the AddLayers dialog
do not fail if someone provides the TMS version as part of the url, also set the title of the store so that we don't see Untitled in the source combo box
if a non-existing style is referenced, use the default style instead, also don't hide the error message
Merge branch 'master' of https://github.com/opengeo/gxp into arcgis_rest
Merge pull request #193 from cga-harvard/arcgis_rest

Display ArcGIS REST layers
Merge pull request #177 from opengeo/projection

Properly set equivalent projection when possible in WMSSource