Added error reporting if evaluateExpression() is given a bad
assignVariableName parameter.

Change-Id: Iebc1ca5f02dac59ee91fc920a24b32db3724cbda
using childrenCreated() instead of creationComplete() to prevent
callbacks from firing after dispose when dispose is called right away.

Change-Id: I27ad0479583aa0880ba7b5ac1b25e203d32b536f
fixed wrong syntax

Change-Id: I827c81fa8e7f28b16543af473f14146b3b63cf52
Refactored WeavePath.js to use prototype, and exposed constructor as
weave.WeavePath.
loadFile() now accepts a JS callback.

Change-Id: I4603e44613779e2110bb446c5a9bcb699298bc71