fix bug 147, cmake support message

[yodalee]

There are two modification.
First is bug 147:
I found that the base problem is that qucs/schematic.cpp pass float argument by a division of two integer, and doesn't add (float) casting.
After adding casting, the resize ratio will not be zero anymore.
Consider cpp style, maybe modify to static_cast is recommended.

Second is cmake supported
Since I cannot compile qucs/qucs on archlinux by autoconf/configure/make, I use cmake to compile the project.
I add some recommended message in README.md and ignore the recommended build path in .gitignore

The last one is ignore vim temporary file .*.swp file

[yodalee]

The printed pdf is not in a good format, I will try to hack on that too.

[guitorri]

I suggest you do your work on branches this way you will not mess with master.
Please try to make a separate PR for each bug or feature. It makes it easier to discuss and faster to merge.
Also note that the Readme is in markdown format, you might want break a line so the commands are rendered in a code block.

I recall you asked about the Qt warning messages. If I run qucs from the terminal/console, the warnings and debug messages should be printed in there.
Note that despite being quite complete, CMake support is still experimental.

[yodalee]

Well, I compile successfully with CMake, and failed by automake tool T_T.
I run into qt issue / c++ namespace when configure qucs, qucs-core, respectively.

---

I will try to create branch to separate fix patch later.

[yodalee]

I will make another PR with branch on each fix. Sorry for whole the mess.