Support the remaining fragment expression types

[markhobson]

The following fragment expressions are currently supported:

• templatename::fragmentname
• templatename::fragmentname(param=value)
• templatename::[domselector] (explicit DOM selector)

We should also support the following:

• templatename::domselector (implicit DOM selector) :white_check_mark:
• templatename :white_check_mark:
• ::domselector
• this::domselector