Drop the markdown/shortcode toggle feature from editor toolbar and update icons (#1636, #1637)

novelwriter/assets/icons/typicons_dark/nw_tb-underline.svg

@@ -1,5 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <svg width="24" height="24" version="1.1" viewBox="0 0 6.35 6.35" xmlns="http://www.w3.org/2000/svg">
- <path d="m3.1782 5.0271q-0.36231 0-0.6547-0.1017-0.28603-0.10806-0.49579-0.33689-0.2034-0.22883-0.31782-0.58479-0.10806-0.36231-0.10806-0.87717v-2.3328h0.73733v2.3899q0 0.33689 0.057206 0.57207 0.063563 0.22883 0.17162 0.36866 0.11441 0.13984 0.26697 0.2034 0.15255 0.057206 0.34324 0.057206 0.19068 0 0.3496-0.057206 0.15891-0.063564 0.27332-0.2034 0.11441-0.13984 0.17798-0.36866 0.063564-0.23519 0.063564-0.57207v-2.3899h0.70555v2.3328q0 0.51487-0.10806 0.87717-0.10806 0.35595-0.31782 0.58479-0.2034 0.22883-0.49579 0.33689-0.28603 0.1017-0.64835 0.1017z" fill="#aeaeae" stroke-opacity=".78039" stroke-width=".47673"/>
- <rect x="1.0583" y="5.2917" width="4.2333" height=".52917" fill="#aeaeae" stroke-width="1.2172"/>
+ <path d="m3.1778 4.846q-0.32417 0-0.58578-0.090994-0.25592-0.096685-0.4436-0.30143-0.18199-0.20474-0.28436-0.52323-0.096684-0.32417-0.096684-0.78483v-2.0872h0.65971v2.1383q0 0.30143 0.051184 0.51185 0.056872 0.20474 0.15355 0.32985 0.10237 0.12512 0.23887 0.18199 0.13649 0.051184 0.30711 0.051184 0.17061 0 0.3128-0.051184 0.14218-0.056873 0.24455-0.18199 0.10237-0.12512 0.15924-0.32985 0.056873-0.21043 0.056873-0.51185v-2.1383h0.63128v2.0872q0 0.46067-0.096685 0.78483-0.096684 0.31848-0.28436 0.52323-0.18199 0.20474-0.4436 0.30143-0.25592 0.090994-0.5801 0.090994z" fill="#aeaeae" stroke-opacity=".78039" stroke-width=".42654"/>
+ <rect x="1.5875" y="5.0271" width="3.175" height=".39688" fill="#aeaeae" stroke-width=".91291"/>
+ <path d="m4.9555 5.5562v-0.43195h0.54619v-3.8986h-0.54619v-0.43195h1.1299v4.7624z" fill="#69c" stroke-width="1.1186"/>
+ <path d="m0.26458 5.5562v-4.7624h1.1299v0.43195h-0.54083v3.8986h0.54083v0.43195z" fill="#69c" stroke-width="1.1186"/>
 </svg>