Refactor the folder ui/viewmodel and ELSeedValidator. Replace RegExpValidator (deprecated) with RegularExpressionValidator.

[kogawulf]

Refactor ui/viewmodel

Determine which files and classes are considered "helper" files/objects and move them into appropriate subfolders.
This requires feedback from other contributors to decide best layout.

Suggested (or to be considered) files -- along with their .h counterparts of course

• currencies
• el_seed_validator
• fee_helpers
• qml_globals
• settings_helpers
• ui_helpers
• window_event_filter

Refactor class ELSeedValidator

• ELSeedValidator inherits from QValidator, and then seems to implement a regular expression validation manually in its validate() method. The validate method contains the allowed regular expression to be checked against.
• Shouldn't this operate in the same way as every other validate method? That is, the regular expression is defined in the QML file, in this case SeedInput.qml.
• So, shouldn't ELSeedValidator simply inherit from RegularExpressionValidator so it can call the parent validate() method to check the regular expression, and then do the extra code in its validate() method?

Refactor RegExpValidator references

RegExpValidator is apparently deprecated and it is recommended to use RegularExpressionValidator

[Maxnflaxl]

@anatolse