Make xtype names of containers case-insensitive

The HST xtype names for containers currently require weird casing (e.g. 'HST.vBox' instead of just 'hst.vbox'). This confuses and annoys many developers (e.g. see the mail thread on the hippo-dev list with subject 'Help wanted for naming a new HST container xtype').

We should make the xtype names case-insensitive. Developers can then simply use, for example, 'hst.vbox' without worrying about the exact casing.

The HST also matches the xtypes names case-insensitive (see class StandardContainerComponent). However, the channel manager still requires exact casing. This should be fixed in the file
factory.js (line 60), where the container type is looked up in a 'registry' map based on the exact name.