Refactoring and find/replace dialog in the JSON editor.

SQL and JSON text editor classes have been refactored. A new parent class
for both editors have been added for the common logic implementable without
depending on the specific lexer.

The only visible effect of this change should be that the JSON editor
(issue #1173) now has the same find/replace dialog as the SQL editor.

This prepares for the implementation of the XML editor (issue #1253).

src/src.pro

@@ -60,7 +60,8 @@ HEADERS += \
     RemoteModel.h \
     RemotePushDialog.h \
     jsontextedit.h \
-    FindReplaceDialog.h
+    FindReplaceDialog.h \
+    ExtendedScintilla.h
 
 SOURCES += \
     sqlitedb.cpp \
@@ -98,7 +99,8 @@ SOURCES += \
     RemoteModel.cpp \
     RemotePushDialog.cpp \
     jsontextedit.cpp \
-    FindReplaceDialog.cpp
+    FindReplaceDialog.cpp \
+    ExtendedScintilla.cpp
 
 RESOURCES += icons/icons.qrc \
              translations/flags/flags.qrc \