[maven-release-plugin] copy for tag learnlib-0.13.0

Synchronize the master branch with the release branch to prevent that the
master branch is ahead by single merge commits. Allows future tags to be
fast-forwarded when reintegrated into the master branch.

add information about continuous deployment

[skip ci]

(cherry picked from commit 705b246)

[skip ci]

(cherry picked from commit b3c7d6b)

[skip ci]

(cherry picked from commit 4d198f3)

(cherry picked from commit 6051c7a)

- remove redundant PROFILE flag
- add method for explicitly querying single (cumulated) profiles
- improve JavaDoc

(cherry picked from commit 81dcf43)

(cherry picked from commit b6795d9)

Fix the behaviour of the `addAlphabetSymbol` method if the learners were
initiliazed with a GrowingAlphabet already.

Previously, due to sharing the alphabet instance with the hypothesis
automaton, caching mechanisms prevented the correct propagation of the new
alphabet symbol.

(cherry picked from commit 87477d8)

Constructors and getters should be package private so that the suspend/resume logic cannot be interferred with.

(cherry picked from commit 8415f9d)

This was required for the sftp upload to a custom FTP server, which has been
removed from the deploy process.

(cherry picked from commit 707ad27)

Also setup travis to clone the corresponding branch of AutomataLib, so that
e.g. building the release branch also uses the release branch of AutomataLib.

(cherry picked from commit d513063)