[FEATURE] Add TypoScript condition for ApplicationContext

The following condition is available in TypoScript and TSconfig
for testing the ApplicationContext:

[applicationContext = value1, value2, ...]

One of the given values matching the applicationContext.
Wildcards + and * are allowed, as well as regular expressions
delimited with /PREG_PATTERN/

Examples:

[applicationContext = Development/Debugging, Development/Profiling]
  # matching exactly "Development/Debugging" or "Development/Profiling"
[global]

[applicationContext = Production*]
  # matching any applicationContext with a rootContext of "Production",
  # for example "Production/Live" or "Production/Staging"
[global]

[applicationContext = /^Production\/Staging\/Server\d+$/]
  # matching "Production/Staging/Server1", "Production/Staging/Server2"
  # and so on
[global]

Resolves: #50132
Documentation: #52701
Releases: 6.2
Change-Id: I4f0f69ca4208d36d8eb8966ec9ef034f6b703b34
Reviewed-on: https://review.typo3.org/22412
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Markus Klein
Tested-by: Markus Klein