Add support for multiline strings

[maguro]

I am shepherding a change in Protobufs to allow multi-line string values:

protocolbuffers/protobuf#1297
protostuff/protostuff-compiler#60

This ticket serves as a marker for the corresponding effort required in this project. I have forked this project and gotten a working version on my fork. I'll submit a PR once things start solidifying in the protobuf project.

[maguro]

Looking good...

[maguro]

The plugin is aware of two kinds of strings, ones that are for string values and ones that are for string names, e.g. import paths:

When a string value is used somewhere a string name is required, the proper error occurs:

[kshchepanovskyi]

This issue is closed as plugin is not supported anymore.
Please switch to https://github.com/jvolkman/intellij-protobuf-editor.