Add support for multiple strings files

[mathebox]

With this PR, it becomes possible to use multiple strings files in a project when using the --extract-loc-strings option. If a NSLocalizedString call specifies a specific table name, the key will be put in the according file.

For example, the usage of NSLocalizedString("key", tableName: "CustomName", comment: "...") will require a CustomName.strings file.

Because of this, a Localizable.strings file is no longer strictly required. Any other .string file will also work.

Fixes #20

Question:
StringsFilesSearch.findAllStringsFiles(within baseDirectoryPath: String, withFileName fileName: String) is currently not used. This method might helpful for future functionality. Should I remove this method anyway?

[mathebox]

Apparently, there is a problem. BartyCrouch tries to localize .strings files of storyboard files. I'll look into this.

[Jeehut]

Hi @mathebox, thank you for this PR. Did you succeed in fixing the issue?

Also, could you please update your commit messages to conform to the contribution guidelines? Mainly you need to remove the dot at the end of your commit messages.

[mathebox]

Hi @Dschee. Yes, I fixed the problem. .strings files are going to be exclude if there is an storyboard or xib files with the same name.

Feel free to use 'merge & squash' for this pull request.

[Jeehut]

@mathebox Thank you for this PR, looks good to me and the tests seem to pass as well. Merging this.

[Jeehut]

Gonna wait a bit and see if #73 is finished soon and release in a few days at the latest.

[Jeehut]

Unfortunately your solution had unexpected side effects. See #11 for more details.