#1544 Support metadata plugin.link for plugins

[Hiroshi Miura]

Since OmegaT 5.3.0 it support plugin metadata that is in jar manifest.
It is nice if OmegaT recognize plugins project URL using Plugin-Link metadata.

FRE#1434 is the ticket to introduce metadata as follows

Data	OmegaT	Manifest	Bundle
Name	Plugin-Name	Implementation-Title	Bundle-Name
Version	Plugin-Version	Implementation-Version	Bundle-Version
Author	Plugin-Author	Implementation-Vendor	Build-By
Description	Plugin-Description	n/a	n/a

I'd like to propose an addition of data.

Data	OmegaT	Manifest	Bundle
Name	Plugin-Name	Implementation-Title	Bundle-Name
Version	Plugin-Version	Implementation-Version	Bundle-Version
Author	Plugin-Author	Implementation-Vendor	Build-By
Description	Plugin-Description	n/a	n/a
Website	Plugin-Link	n/a	n/a

It is also nice that a table on Properties->Plugins would have a hyperlink to specified project website.
User can easily check an update of plugins and see plugin manuals using this link.

[Hiroshi Miura]

Proposed patch at https://github.com/omegat-org/omegat/pull/92

[Hiroshi Miura]

https://github.com/omegat-org/omegat/pull/92 proposes following three type of data.

• PLUGIN_CATEGORY = "Plugin-Category"
• PLUGIN_LINK = "Plugin-Link"
• PLUGIN_TYPE = "OmegaT-Plugin"

[Hiroshi Miura]

Improvement has been merged in master as ccbfe727