Node-by-node control of node rendering ("nodeless" mode)

[dan-knight]

Description

Allows node-by-node control of node ellipse drawing with a draw.nodes column in the tree input data frame. This was previously handled globally with an argument of the same name on SRCGrob. Also includes unit-tests and new examples in the package manual and User Guide vignette.

Example

nodeless <- data.frame(
    parent = c(
        NA, 1, 2, 2, 2, 
        3, 3, 3, 
        4, 4, 4, 4, 4, 
        5, 5, 5, 5
        ),
    draw.node = TRUE,
    spread = NA
    );
nodeless$spread[6:nrow(nodeless)] <- 0.6;
nodeless$draw.node[c(2, 6:nrow(nodeless))] <- FALSE;

grid.draw(SRCGrob(nodeless));

Checklist

• [x] This PR does NOT contain Protected Health Information (PHI). A repo may need to be deleted if such data is uploaded.
  Disclosing PHI is a major problem[^1] - Even a small leak can be costly[^2].

• [x] This PR does NOT contain germline genetic data[^3], RNA-Seq, DNA methylation, microbiome or other molecular data[^4].

[^1]: UCLA Health reaches $7.5m settlement over 2015 breach of 4.5m patient records [^2]: The average healthcare data breach costs $2.2 million, despite the majority of breaches releasing fewer than 500 records. [^3]: Genetic information is considered PHI. Forensic assays can identify patients with as few as 21 SNPs [^4]: RNA-Seq, DNA methylation, microbiome, or other molecular data can be used to predict genotypes (PHI) and reveal a patient's identity.

• [x] This PR does NOT contain other non-plain text files, such as: compressed files, images (e.g. .png, .jpeg), .pdf, .RData, .xlsx, .doc, .ppt, or other output files.

  To automatically exclude such files using a .gitignore file, see here for example.

• [x] I have read the code review guidelines and the code review best practice on GitHub check-list.

• [x] I have set up or verified the main branch protection rule following the github standards before opening this pull request.

• [x] The name of the branch is meaningful and well formatted following the standards, using [AD_username (or 5 letters of AD if AD is too long)]-[brief_description_of_branch].

• [x] I have added the major changes included in this pull request to the CHANGELOG.md under the next release version or unreleased, and updated the date.

[dan-knight]

Looks good to me but I think there's some lint fixes to be done?

Fixed!