Removed old ICAT interface classes. Refs #8274.

- Removed relevant classes from cmake list.
Removed advancedSearch from application window. Refs #8274.
Removed MyDataSearch from application window. Refs #8274.
Removed ICatSearch from application window. Refs #8274.
Renamed ICatHelper class. Refs #8274.
Renamed ICatSearch class. Refs #8274.

- Renamed `Login` `search`, and `logout` variables in `ApplicationWindow.cpp` to be ICAT independant.
- Renamed relevant interface class to match related class name.
- Updated CMakeLists.
Refs #8343 Fixed error and refactored code.

Also modified the interface code to only allow the user to input a valid
min/max value.
Added algorithm helper class. Refs #8322.

- This class reduces the code across algorithms.
Refactored `CatalogSearch`. Refs #8322.

- Removed unused attributes from `CatalogSearchParam`.
- Updated `ICat3Helper.cpp` to work correctly with new interface (e.g. when "my data" is checked).
- Updated documentation for algorithm.
Refs #8311 Fix scale multiplier still being enabled.
Tidied `CatalogSearchParam` class. Refs #8322.

- Removed unnecessary comments in header. Made them more concise and consistent with other header files in Mantid.
- Removed RB number search as it is no longer used in the interface.
- Added investigator surname search back to `CatalogSearch`.
Tidied up `CatalogMyDataSearch`. Refs #8322.

- Removed unused headers and added call to helper class.
Refactored catalog logout algorithm. Refs #8322.

- Removed unimplemented method `doLogout()`.
Tidied Catalog login algorithm. Refs #8322.

- Removed unnecessary catalog error method.
Updated CatalogListInstruments. Refs #8322.
Made use of algorithm helper class. Refs #8322.

- Removed unused methods (`filterLogFiles` & `isDataFile`) and related properties.
Use algorithm helper class. Refs #8322.

- Updated documentation for each algorithm and tidied header files.
Updated `CatalogDownloadDataFiles`. Refs #8322.

- Added call to helper class and removed un-used headers.
- Removed `using` Poco namespaces as each are only called once or twice in the download method.
Refs #8343 Fix for system test
Refs #8343 Rewritten slice functions to account for monitors.