Add custom token management

[redDwarf03]

Description

Fixes #1160

Type of change

• New feature (non-breaking change which adds functionality)

Material used:

Please delete options that are not relevant.

• iOS (Smartphone/Tablet)

How Has This Been Tested?

• Add / Hide custom tokens
• In add custom sheet, search token by address or directly in the user's balance
• In swap sheet, search token by address or in custom list

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Useful info for the reviewer:

[Chralu]

Idealement, prendre 30 min pour faire des TU sur cette methode.