Fix instantiation check problem with < char

[PhilippImhof]

Currently, the instantiation check in the edit form can fail if the variable definition contains the < char. This is, because we currently use PARAM_TEXT and this does not support the < char despite the Moodle docs stating otherwise.

We will now use PARAM_RAW and solve that problem. The PR adds a test case to the unit test.

[coveralls]

Pull Request Test Coverage Report for Build 7477244568

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 75.03%

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Totals
Change from base Build 7245735740:	0.0%
Covered Lines:	2524
Relevant Lines:	3364

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💛 - Coveralls