Adds functionality to create pre-populated text fields.

Adds functionality to create pre-populated text fields, and support
for negative and decimal numbers in typeblocks.

Change-Id: I13024240b2ba2fb69ac01d4d7b394ab7ade3502a
Re-arrange typeblocks.js to place the constructor first.

The constructor must be the first item in the file when the code is
compiled by the Closure Compiler.

Change-Id: I59b031191a0728fb9266c640c205ccf12acad2cf