RC link validation

[da1nerd]

Story

As a user I want rc links to be validated so that I know to fix broken links.
Links must adhere to the specification outlined at http://resource-container.readthedocs.io/en/latest/linking.html.

Notes

The bad links should be listed in the warning dialog on the Door43 page for the project.

Example

For example there are a whole bunch of broken links in tl_tn. See links.txt for a list of invalid links and their file locations.

To illustrate, here's a sample broken link from the uploaded file:

// found in 1ch/01/01.md
[[rc://tl/bible/questions/comprehension/1ch/01]]

The proper form of this link is the following:

[[rc://tl/tq/help/1ch/01/01]]

Validation

The link requirements are described at http://resource-container.readthedocs.io/en/latest/linking.html.
Below is a basic illustration of a valid link structure.

rc://[language code]/[resource id]/[book|help|dict|man|bundle]/...

Without checking against all available resources (a potentially time consuming task) we could assert that the third path position be a value in the set [book, help, dict, man, bundle]. e.g. rc://.../.../book.
This will leave the language code and resource id susceptible to invalid values, however I believe such cases will be rare when the resource type has been properly indicated.