Unit tests are suspicable to rounding errors

[p-snft]

The unit tests for solar thermal use lp files that contain decimal representations of floating point numbers. The actual values seem to depend on the used platform, so the unit test worked for me but failed at Travis. (I now fixed it to fail at my computer, see 7dd83ea)

[c-moeller]

We also had this problem in the past. Don't know how we could handle this well.

[sasanjac]

The instance that generates and verifies the lp files should round the values before saving. The tests can then check against these rounded values.