#563 - add icons for all modal buttons

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

src/main/resources/templates/categories/categories.ftl

src/main/resources/templates/charts/manage.ftl

src/main/resources/templates/filter/filterMacros.ftl

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

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

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

src/main/resources/templates/templates/templates.ftl

src/main/resources/templates/transactions/transactions.ftl

src/main/resources/templates/whatsNewModal.ftl