Generalize Dockerfile, add 8.1.1

[3nprob]

Adds release 8.1.1.

Also, I took the liberty to restructure a bit since the directories are pretty much identical save for the URLs and version numbers.

Adds new environment variable TIGASE_DOCKER_IMAGE that can be changed to build against custom registries.

build script should behave like previously by default.

[woj-tek]

Hi,
thank you for your effort and contribution.

In order for us to proceed with it we require "Source Code Disclaimer" - if you agree with it please submit a message/comment to this PR stating that: "You submit your source code and allow Tigase to release the code as a part of Tigase's own software package under any license, either an open source or closed source."

As for the PR itself: yes, Dockerfiles are almost identical, but we opted to have dedicated configurations to avoid issues if there would be some small change in future versions. It may be sensible to group those similarities within minor versions though (8.0, 8.1, 8.2, etc) and if you are willing you can adjust your changes to fit that patter.

Second thing - please split version addition (8.1.1 - a fault on our part) from the structure changes).

[3nprob]

Thanks for the quick reply!

In order for us to proceed with it we require "Source Code Disclaimer" - if you agree with it please submit a message/comment to this PR stating that: "You submit your source code and allow Tigase to release the code as a part of Tigase's own software package under any license, either an open source or closed source."

Before that, would you mind clarifying the license situation? tigase-server is and will continue to be under Affero GPL, correct? So this license-ambivalence is just concerning this specific repo?

Second thing - please split version addition (8.1.1 - a fault on our part) from the structure changes).

Not sure what you mean by this (split version addition)

[arthef]

Thanks for the quick reply!

In order for us to proceed with it we require "Source Code Disclaimer" - if you agree with it please submit a message/comment to this PR stating that: "You submit your source code and allow Tigase to release the code as a part of Tigase's own software package under any license, either an open source or closed source."

Before that, would you mind clarifying the license situation? tigase-server is and will continue to be under Affero GPL, correct? So this license-ambivalence is just concerning this specific repo?

Technically speaking, once software is released under GPL/AGPL, there is no way to change it's license. I mean, this particular code version at certain commit point.
However, the software license could be changed in future versions, theoretically I mean. We do not have any plan for this at the moment, however we offer Tigase under a dual-licensing model for customers who need a different licensing terms than AGPL. Therefore, we must have full freedom over the source code and possible license terms.

[woj-tek]

Not sure what you mean by this (split version addition)

Please make two PR:

• one with changes related to organisation (generalisation per version 8.0, 8.1, 8.2)
• one with inclusion of new version (8.1.1) I actually included it already