Switched some warning messages from deprecated function to boost::format

[markus-jehl]

The deprecated warning function ignores verbosity. Therefore, this PR is switching selected calls over to the new warning function.

Changes in this pull request

Changed some calls to deprecated warning function to new warning function using boost::format.

Testing performed

Built and loaded proj data object that triggered some warnings. After changing verbosity these warnings were no longer printed.

Related issues

fixes some instances of #1286

Checklist before requesting a review

• I have performed a self-review of my code
• [] I have added docstrings/doxygen in line with the guidance in the developer guide
• [] I have implemented unit tests that cover any new or modified functionality (if applicable)
• The code builds and runs on my machine
• [] documentation/release_XXX.md has been updated with any functionality change (if applicable)

[KrisThielemans]

It's a bit unfortunate to have to explicitly cast to std::string. What about adding another overload

void warning(const char * const m) { warning(std::string(m)); }

or something similar as work-around. This would catch all instances that don't have extra arguments without needing to change the actual code.

[markus-jehl]

Sure, that's fine with me as well. Will change.

[markus-jehl]

unfortunately it doesn't compile because it says the call to "warning" is ambiguous: it doesn't know which deprecated function to call...
I would propose to keep this PR as is and then remove the deprecated implementation once and for all after the TOF merge.