Details:
* Improved unsafe C-style macros inheritance approach to the project-wide
DEFINES: it is unspecified in
which order source files are being preprocessed ones, so in
singleapplication.cpp the class might be inherent of default-specified
base, while in main.cpp this can be a user-provided QAPPLICATION_CLASS
definition.
* Replace Qt's pseudo-keywords to more library-independent counterparts
('emit -> Q_EMIT', etc)
* Indentation fixes (80 character column-width)
* Rearragned #include statements: from most platform-independen to more
app-specific.
* Fixed some grammar typos.
* README.md updated respectively.
