Use strings to store SlaveTemplate references in EC2Slave.

When EC2Slave objects are persisted, references to the SlaveTemplate
that was used to provision them are broken unless the template's name
itself is stored.
Merge branch 'template-instance-cap-fix'

Conflicts:
	src/main/java/hudson/plugins/ec2/EC2Slave.java
Move documentation comment to correct place.
Merge branch 'template-node-name'

Conflicts:
	src/main/java/hudson/plugins/ec2/EC2Slave.java
Bump version.