#593 - refactor: generic ids and css classes for image select

src/main/resources/static/css/accounts.css

src/main/resources/static/css/style.css

src/main/resources/static/js/imageSelect.js

src/main/resources/templates/accounts/accountFunctions.ftl

src/main/resources/templates/accounts/newAccount.ftl

src/main/resources/templates/helpers/availableImages.ftl

src/main/resources/templates/helpers/imageSelect.ftl