scrappers for upcomming federal elections

[adibender]

• Sachsen
• Brandenburg
• Thüringen

[bauer-alex]

On the devel branch, Brandenburg and Thüringen work out well.
For Sachsen sometimes the sample size isn't extracted correctly. For the Infratest polls from 02.07.2019 and 28.08.2018, the function outputs n=100 instead of 1000.

Reason for this is that these instances comprise two blanks after the dot in the Befragte field of the Wahlrecht table (only visible when read into R) instead of only one blank.

Base call:
scrape_ltw("http://www.wahlrecht.de/umfragen/landtage/sachsen.htm", ind_row_remove = -c(1))