#282 Add time formatting functions

[Erik Hänel]

For enhancing the possibilities to analyze log files, the addition of time formatting functions would be helpful, i.e. add the two functions

to_time("TIME_FORMAT", "TIME") -> VAL
timeformat("TIME_FORMAT", TIMEVAL) -> STR

where "TIME_FORMAT" will contain the usual identifier chars yMdHms, where M means "month" and m means minute, and of course the used separators, e.g. yyyy-MM-dd HH:mm:ss.

Analysis:
The function to_time() will be classified as STR_STR type and timeformat() will be STR_VAL as type. The function to_time() will need the tm struct and the mktime() function from <ctime>. timeformat() can be implemented similar to the already available date() function.

Implementation:
The two functions were implemented as proposed by the analysis. Implementation tests were passed successfully.

Documentation:
The functions were added to the language files, to the syntax elements and to the find database.

Tests:
The functionality was added to the automatic tests. No deviations detected. Functionality implemented successfully.