Revisit language consistency, menu item locations

Some menu entries, actions, etc. could be renamed/relocated to be more concise and consistent:

• move Account -> New Credit Transfer to Transaction -> New Online Transfer
• main panel's Outbox to Online Transfers
• "Combine" and "Match" are used interchangeably in documentation. However, looking at the code, these have (or intended to have) a separate meaning.
• move Edit -> Find Transaction to Transaction -> Find
• Find Transaction opens Search transactions dialog
• rename Equities to Securities (or Positions?)
• address the Currencies..., Prices... and Update Stock and Currency Prices... confusing options in Tools
• Map account is too generic, maybe Configure online banking?
  • Unmap account is redundant; Configure online banking should have an option to disable/reset the mapping
• Update account is too generic, maybe Download transactions?
• address the confusing Use Finance::Quote and Online Source options in security details dialog.
• add QFX to OFX position in File -> Import
• Ledger in Settings to Ledgers to match the main side panel
• Show Balance Chart -> Balance Chart
• Asset -> Assets, Liability -> Liabilities in Accounts view
• Chart/Report -> Show Chart/Show Report in Reports view
• New account -> New sub-account in right click menu in accounts view (and make the dialog automatically preselect parent account)
• Remove New category from right click menu in Accounts view
• Merge in Payees, but Match in Ledger
• Move all the debugging actions to a separate Debug menu
• Enable all messages is too vague, use something like Reset hidden messages settings
• Scheduled transactions panel -> Scheduler
• Reorder panel items according to the frequency of usage and common sense: Home, Institutions, Accounts, Categories, Ledgers, Investments, Forecast, Budgets, Outbox, Payees, Tags
• Update on Payees view should be Save, or Accept, to match with other views.
• We use KBanking interchangeably with AqBanking. I think using KBanking may be confusing and unnecessary. Since we already have Weboob (Woob) and do not rebrand it into something KMyMoney-esque, we should also stick to using AqBanking only. This also helps users realize that AqBanking is an external project, otherwise not managed by KMM team (not explicitly).
• In QIF importer/exporter, rename filter to preprocessor.
• In Split editing dialog, right clicking on a split shows "Delete", but "Clear" is used elsewhere in the dialog. Clear doesn't make sense here: we're not "clearing" the splits (their contents, e.g. category and/or amount) and otherwise leaving them in-place, but we're actually removing them.
• Preferred accounts <-> Favorite Accounts