Use position number for expressions in babel-plugin-c-3po

[AlexMost]

The global configuration option - useNumberedExpressions, that will use position number for expressions in translations instead of variable names. This option will allow using complex expressions inside translations like:

Option

name - useNumberedExpressions default value - false

configuration

{ "useNumberedExpressions": true } 

Example extract

t`Hello ${ getUserName() }`

will be extracted to

msgid: "Hello ${ 0 }"
msgstr: ""

Example resolve

t`Hello ${ getUserName() }`

msgid: "Hello ${ 0 }"
msgstr: "Привет ${ 0 }"

will be resolved to:

`Привет ${ getUserName() }`

Roadmap

• [x] implement global setting
• [x] extract logic
• [x] resolve logic
• [x] tests for t,jt,gettext,ngettext

Prerequisite for this issue https://github.com/c-3po-org/c-3po/issues/95

[AlexMost]

this task is already done and available in the preminor version of plugin 0.8.0-0 for test.