Add tags feature

* show the tags in the entry preview
* allow searching by tag
* add a sidebar listing the tags in the database
* filter entries by tag on click
* Introduce a new TagsEdit widget that provides pill aesthetics, fast removal functionality and autocompletion
* add tests for the tags feature
* introduce the "is" tag for searching. Support for weak passwords and expired added.

src/gui/entry/EditEntryWidgetMain.ui

@@ -56,7 +56,7 @@
     <property name="verticalSpacing">
      <number>8</number>
     </property>
-    <item row="6" column="1">
+    <item row="7" column="1">
      <layout class="QVBoxLayout" name="verticalLayout_2">
       <item>
        <widget class="QPlainTextEdit" name="notesEdit">
@@ -99,7 +99,7 @@
       </property>
      </widget>
     </item>
-    <item row="6" column="0">
+    <item row="7" column="0">
      <layout class="QVBoxLayout" name="verticalLayout">
       <item>
        <widget class="QCheckBox" name="notesEnabled">
@@ -129,7 +129,7 @@
       </item>
      </layout>
     </item>
-    <item row="5" column="1">
+    <item row="6" column="1">
      <layout class="QHBoxLayout" name="horizontalLayout_2">
       <property name="spacing">
        <number>8</number>
@@ -252,7 +252,7 @@
       </property>
      </widget>
     </item>
-    <item row="5" column="0">
+    <item row="6" column="0">
      <layout class="QHBoxLayout" name="horizontalLayout">
       <property name="spacing">
        <number>0</number>
@@ -272,6 +272,26 @@
       </item>
      </layout>
     </item>
+    <item row="5" column="0">
+     <widget class="QLabel" name="tagsLabel">
+      <property name="text">
+       <string>Tags:</string>
+      </property>
+      <property name="alignment">
+       <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+      </property>
+     </widget>
+    </item>
+    <item row="5" column="1">
+     <widget class="TagsEdit" name="tagsList" native="true">
+      <property name="focusPolicy">
+       <enum>Qt::StrongFocus</enum>
+      </property>
+      <property name="accessibleName">
+       <string>Tags list</string>
+      </property>
+     </widget>
+    </item>
    </layout>
   </widget>
  </widget>
@@ -288,12 +308,19 @@
    <header>gui/URLEdit.h</header>
    <container>1</container>
   </customwidget>
+  <customwidget>
+   <class>TagsEdit</class>
+   <extends>QAbstractScrollArea</extends>
+   <header>gui/tag/TagsEdit.h</header>
+   <container>1</container>
+  </customwidget>
  </customwidgets>
  <tabstops>
   <tabstop>titleEdit</tabstop>
   <tabstop>usernameComboBox</tabstop>
   <tabstop>passwordEdit</tabstop>
   <tabstop>urlEdit</tabstop>
+  <tabstop>tagsList</tabstop>
   <tabstop>fetchFaviconButton</tabstop>
   <tabstop>expireCheck</tabstop>
   <tabstop>expireDatePicker</tabstop>