Perf batch 1 v5

[timcadman]

Description of changes

• Refactored absDS, asDataMatrixDS, asIntegerDS, listDS, asLogicalDS, asMatrixDS and asNumericDS.
• Created serverside function expDS and logDS as these previously didn't exist.
• Extended .loadServersideObject to handle both object names and column names as input.
• Added performance tests.
• Updated test expectations following refactor.

Instructions & checklist for PR reviewers

Code review

• Check that object is loaded via .loadServersideObject and not with eval.
• Check that if class checks were previously present on the clientside they have been added to the serverside.
• Check that performance tests have been added for all functions unless they already existed.
• Check tests have been updated to reflect changed expectations.

Testing

• Clone dsBaseClient using branch perf-batch-1.
• Install dsBase on a test server based on this branch.
• Run devtools::test( ) on the clientside package and check all tests pass
• Run devtools::build( ) on the clientside package and check it builds without errors
• Run devtools::test( ) on the serverside package and check all tests pass
• Run devtools::build( ) on the serverside package and check it builds without errors