title: split character columns and get names of field in string
body: <p>I need to split a column that contains information into several columns.<br>
  I'd use <code>tstrsplit</code> but the same kind of information is not in the same order among the rows and I need to extract the name of the new column within the variable. Important to know: there can be many pieces of information (fields to become new variables) and I don't know all of them, so I don't want a "field by field" solution.   </p>
  
  <p>Below is an example of what I have:</p>
  
  <pre><code>library(data.table)
  
  myDT &lt;- structure(list(chr = c("chr1", "chr2", "chr4"), pos = c(123L,
                    435L, 120L), info = c("type=3;end=4", "end=6", "end=5;pos=TRUE;type=2"
                    )), class = c("data.table", "data.frame"), row.names = c(NA,-3L))
  
  #    chr pos                  info
  #1: chr1 123          type=3;end=4
  #2: chr2 435                 end=6
  #3: chr4 120 end=5;pos=TRUE;type=2
  </code></pre>
  
  <p>And I'd like to get:</p>
  
  <pre><code>#    chr pos end  pos type
  #1: chr1 123   4 &lt;NA&gt;    3
  #2: chr2 435   6 &lt;NA&gt; &lt;NA&gt;
  #3: chr4 120   5 TRUE    2
  </code></pre>
  
  <p>A most straightforward way to get that would be much appreciated! (<em>Note: I'm not willing to go with a dplyr/tidyr way</em>)</p>